1. Field of the Invention
The present invention relates to a communication system, apparatus, method, and recording medium for mobile communication and, more particularly, to a communication system, apparatus, method, and recording medium which can perform stable communication by changing the data transfer rate in accordance with the moving speed of mobile communication terminal apparatus (to be simply referred to as a mobile terminal hereinafter).
2. Description of the Prior Art
As a next-generation mobile communication system, a high-speed, large-capacity system called the IMT-2000 has recently been studied. This system is claimed to realize a maximum data transfer rate of 2 Mbps, which is incomparably higher than those of existing mobile communication systems.
However, data cannot be unconditionally transferred at 2 Mbps, and some limitation is imposed on the maximum data transfer rate in accordance with the moving speed of a mobile terminal. This is because, as the moving speed of the mobile terminal increases, the number of times of handoffs (the function of guaranteeing the continuity of communication across the zone or cell covered by one base station) increases, and a larger impact is exerted on the system. More specifically, it is expected that the maximum data transfer rate becomes 2 Mbps at a low moving speed; 384 Kbps at an intermediate moving speed; and 64 Kbps at a high moving speed.
In conventional mobile communication, however, even if a mobile terminal is moving at a high speed, a data transfer rate exceeding the maximum data transfer rate corresponding to the moving speed is required. In an extreme case, it is required to communicate data at a maximum data transfer rate of 2 Mbps. As a consequence, handoffs often occur, and a larger impact is exerted on the system. The reason why such a reckless attempt is made is that the system does not have an arrangement for measuring the moving speed of a mobile terminal and performing control to communicate data at a maximum data transfer rate corresponding to the moving speed.
The present invention has been made in consideration of the above situation in the prior art, and has as its object to provide a communication system, apparatus, method, and recording medium for mobile communication, which can perform stable communication regardless of the number of times of handoffs by changing the data transfer rate in accordance with the moving speed of a mobile terminal.
In order to achieve the above object, according to the first aspect of the present invention, there is provided a mobile communication system in which communication is performed between a base station and a mobile communication terminal apparatus, comprising a mobile communication terminal apparatus having a transmission/reception section for transmitting/receiving data between the base station and the mobile communication terminal apparatus, a measuring section for measuring a moving speed of the mobile communication terminal apparatus, and a data transfer rate designation section for instructing the base station to change a data transfer rate in communication in accordance with a moving speed of the mobile communication terminal apparatus which is measured by the measuring section, and a base station for controlling the data transfer rate to perform communication at the data transfer rate designated by the mobile communication terminal apparatus.
In order to achieve the above object, according to the second aspect of the present invention, there is provided a mobile communication apparatus for a mobile communication terminal apparatus for performing communication through a base station, comprising a transmission/reception section for transmitting/receiving data between the base station and the mobile communication terminal apparatus, a measuring section for measuring a moving speed of the mobile communication terminal apparatus, and a data transfer rate designation section for instructing the base station to change a data transfer rate in communication in accordance with a moving speed of the mobile communication terminal apparatus which is measured by the measuring section, wherein communication with the base station is performed at a data transfer rate permitted in accordance with the moving speed of the mobile communication terminal apparatus.
The communication apparatus according to the second aspect further comprises a satellite reception section for receiving electric waves from a plurality of measurement satellites, and the measuring section calculates a current position of the mobile communication terminal apparatus at predetermined time intervals from the electric waves received by the satellite reception section, and measures the moving speed of the mobile communication terminal apparatus on the basis of changes in calculated current position over time.
In addition, the communication apparatus according to the second aspect further comprises a storage section storing a table in which the moving speed of the mobile communication terminal apparatus which is measured by the measuring section is stored in correspondence with a maximum data transfer rate permitted in accordance with the moving speed, reads out a permitted maximum data transfer rate corresponding to the moving speed measured by the measuring section from the storage section, and instructs the base station through the data transfer rate designation section to perform communication at the permitted maximum data transfer rate.
Furthermore, the communication apparatus according to the second aspect further comprises an input section for inputting a data transfer rate, and instructs the base station through the data transfer rate designation section to make a change to the data transfer rate input by the input section when the data transfer rate input by the input section is lower than a permitted maximum data transfer rate corresponding to the moving speed measured by the measuring section.
In order to achieve the above object, according to the third aspect of the present invention, there is provided a communication method of performing communication between a base station and a mobile communication terminal apparatus, comprising the transmission/reception step of transmitting/receiving data between the base station and the mobile communication terminal apparatus, the measuring step of measuring a moving speed of the mobile communication terminal apparatus, the data transfer rate designation step of instructing the base station to change a data transfer rate in communication in accordance with the moving speed of the mobile communication terminal apparatus which is measured in the measuring step, and the communication step of performing communication at a data transfer rate permitted in accordance with the moving speed of the mobile communication terminal apparatus.
In order to achieve the above object, according to the fourth aspect of the present invention, there is provided a recording medium on which a program for executing the communication method according to the third aspect is recorded.
As is obvious from the above aspects, in the communication system, apparatus, method, and recording medium for mobile communication of the present invention, when data is to be transmitted/received between a mobile terminal and a base station, the moving speed of the mobile terminal is measured, and a command is output to the base station to change the data transfer rate in communication in accordance with the measured moving speed, thereby performing communication with the base station at a data transfer rate permitted in accordance with the moving speed of the mobile terminal. This allows stable communication without increasing the impact on the system even with an increase in the number of times of handoffs.
The above and many other objects, features and advantages of the present invention will become manifest to those skilled in the art upon making reference to the following detailed description and accompanying drawings in which preferred embodiments incorporating the principles of the present invention are shown by way of illustrative examples.